Submersible electric motors may be utilized to drive Electrical Submersible Pump (ESP) systems used in the production of oil and water from wells. Submersible electric motors are typically comprised of a housing that houses a stator and a rotor. The rotor is concentrically located within the stator and can rotate during operation. The motor is filled with oil to lubricate the motor and provide heat removal during the operation of the motor. Typically the stator is constructed of multiple metallic laminations that form the stator stack. A pair of thick end laminations, one at each end of the stator stack, interface with a pair of retainer or snap rings, one at each end of the stator stack, to hold the stator stack in place. The thick end laminations and stator laminations have slots through which wires are wound in a conventional manner and into which epoxy or varnish can be introduced. The wound wires form windings that can be energized by a supply of electrical current to create an alternating electromagnetic field. As the windings enter and exit the slots during threading, they form end coils at each end of the stator.
In addition to acting as a moisture barrier and providing a layer of insulation, the varnish also supports the weight of the windings and prevents the end coils from moving. During operation, varnish acts to prevent the end coils from moving inwards toward the rotor and prevents the windings from moving down into the slots. However the varnish impregnation process is expensive and time consuming and makes the motor oil less efficient at removing heat from the windings in the slots and from the end coils. The varnish is also temperature limited and thus limits the conditions into which a motor can be introduced. Further, as the varnish ages, the varnish can flake and contaminate the motor oil, degrading the oil's ability to lubricate and remove heat.
A need exists for a technique that addresses the limitations and shortcomings described above. In particular a need exists for a technique to allow for restraining the end coils without the use of varnish and in a manner that makes motor fabrication less labor intensive and less temperature limited. The following technique solves these problems.